BIOMATERIALS UDC 615.46:546.41’18 A NEW GENERATION OF CALCIUM PHOSPHATE BIOMATERIALS: THE ROLE OF PHASE AND CHEMICAL COMPOSITIONS V. I. Putlyaev 1 and T. V. Safronova 1 Translated from Steklo i Keramika, No. 3, pp. 30 – 33, March, 2006. Calcium phosphate materials are increasingly applied in the treatment and replacement of bone tissues. The effect of their phase and chemical (ionic) composition on biomedical properties (bioresistivity and bioresorption) of such materials is considered. The principles of the formation of bioceramic microstructure, as well as possible directions for chemical modification of calcium phosphates using biocompatible anions and cations, are discussed. Hydroxyapatite (HAP) is a calcium phosphate compound constituting the mineral component of the bone. Since cal- cium and phosphor are the main elements of bones, materials based on calcium phosphate compounds are now used to treat bone tissue defects. Such materials have to meet certain requirements: – they should be biocompatible with the living organism; – depending on the treatment method used, the material should have a certain level of bioresistivity or a certain bio- degradation rate; – in the perfect case, the material should possess biolo- gical activity, i.e., have an osteostimulating effect initiating the formation of bone tissue; – the materials should have a certain strength; – the materials should withstand various types of steri- lization and radiation (UHF, SHF, UV, x-ray, gamma radia- tion) without changing their properties of biocompatibility, bioresistivity, biodegradability, bioactivity, and strength pa- rameters; – porous materials should meet certain requirements on the type of porosity and the size of pores, whose diameter should be at least 100 mm, and ensure the desired interaction between the body and the implanted material, i.e., the in- growth of blood vessels and nerve fibers into the implant; – osteoplastic materials should be easily amenable to mechanical treatment or other shape-correcting method used in surgery. Most materials in the CaO – P 2 O 5 –H 2 O system easily satisfy the requirement of biocompatibility. The presence in the material of CO 3 2- , SiO 4 4- , Cl – ,F – , Na + ,K + , Mg 2+ , etc., i.e., all ions contained in the natural bone structure or in body tissues, do not disturb biocompatibility. A biologically compatible material implemented in a liv- ing organism does not have a negative effect on tissues, therefore, such implant is not rejected. Based on their effect on body tissues, biocompatible ma- terials can be classified as biotolerant, bioinert, or bioactive. Classification of biocompatible materials based on their effect on body tissues Biotolerant.............. Metal alloys, polymers Bioinert ................. Materials based on aluminum oxide, zirconium dioxide Bioactive ................. Materials based on calcium phosphates The effect of body tissues on implanted materials may differ; accordingly, materials can be classified into biode- gradable, bioresistive, and bioresorptive. Classification of biocompatible materials based on the effect of body tissues on materials Biodegradable ............ Metal alloys, polymers Bioresistive ....... Materials based on hydroxyapatite Bioresorptive .... Materials bearing tricalcium phosphate or phosphate and silicophosphate glasses Biodegradability implies the gradual degradation of the structure and properties of a material, and its processing (dis- solution) under the effect of the body fluid. Bioresistivity is Glass and Ceramics Vol. 63, Nos. 3 – 4, 2006 99 0361-7610/06/0304-0099 © 2006 Springer Science+Business Media, Inc. 1 M. V. Lomonosov Moscow State University, Moscow, Russia.